High-Intensity Interstitial Ultrasound for Thermal Ablation of Uterine Fibroids. Benign uterine tumors (fibroids) are clinically apparent in up to 50% of women and typically require surgical removal of symptomatic fibroids or hysterectomy. Treatment options for women considering bearing children are limited to the invasive surgical open myomectomy to best maintain structural integrity of the uterine wall; the less invasive laparoscopic removal is contraindicated. There remains a substantial clinical need for a minimally-invasive alternative to traditional surgical approaches with the promise of less morbidity and recovery time, faster procedure time, and lower cost. Recent clinical investigations of minimally-invasive thermal techniques (cryotherapy, thermal ablation) have demonstrated significant potential in reducing fibroid volume and related symptoms, while preserving uterine wall integrity. Some limitations of these techniques include an inability to spatially control the distribution of energy output to conform to the fibroid volume, inadequate single treatment volumes requiring multiple device insertions, long procedural times, or use may be limited by the proximity of a fibroid to critical tissue structures. Interstitial ultrasound devices are an innovative technology under development by our group for delivering thermal therapy for treating cancer and prostate BPH, with demonstrated capabilities to provide dynamic spatial control of selective heating patterns, greater radial thermal penetration, and fast heating times. We propose to develop this ultrasound technology specifically for the treatment of uterine fibroids; this technology has potential to provide a superior minimally-invasive heating technique for treating uterine fibroids with the promise of more accurate and thorough targeting, protection of critical non-targeted tissue (e.g., bladder, bowel), more accessibility to a larger number of fibroids, and faster procedure times. The objective of this STTR Phase I research plan is to extend existing technology and develop new interstitial ultrasound applicator designs with high-power output, temperature/dose feedback, and spatial control capabilities specific for conformal thermal ablation of large volumes required for successful treatment of uterine fibroids. Empirical design, bench experiments, biothermal and acoustic modeling, together with experimental testing in human uterine fibroid tissue will be used for design feedback and to characterize device performance, as well as assess the technical and potential clinical feasibility. These results will be applied to the conceptual development and understanding of potential treatment approaches in preparation for the ultimate goal of product development and clinical implementation during Phase II. Project Narrative (Relevance). Benign uterine fibroid tumors affect millions of women each year in the U.S. (and around the world), and are the cause of more than half of the 600,000 hysterectomies performed annually in the U.S. There is a true clinical need for effective therapy with improved quality of life that is more favorable than existing treatment options. Direct costs for fibroid treatments exceed $2 billion annually in the U.S. The estimated prevalence of uterine fibroids is 25-50% of women of reproductive age (target age range: 25-54 years old), corresponding to 16-32 million women in the U.S. There are nearly 2 million new cases diagnosed each year. Many women who wish to retain their uterus undergo a major surgical procedure to treat their fibroids. Currently, the only minimally-invasive treatment is uterine artery embolization, which has significant side effects that go beyond the uterus and are also not an option for women who desire future childbearing due to the vascular changes the embolization produces. The proposed new therapeutic ultrasound treatment would avoid major surgery for these women as well as allow them to return to work and activities much faster. In all likelihood, it would allow women to pursue reproduction as well. Further, this new treatment will likely result in far less side effects and complications than any current procedure for fibroids. The target population for acoustic therapy consists of a sizeable fraction of the hysterectomy patients, all patients who would be treated by embolization, nearly all of those that would otherwise have had myomectomy, and conservatively 20-25% of those who now have nothing done. [unreadable] [unreadable] [unreadable]